German police have opened an investigation into an unidentified female who called in a bomb threat during the live final of a modelling competition, prompting broadcaster ProSieben to stop the show.

Thousands of people were evacuated from the SAP Arena in the southwestern German city of Mannheim, where German model Heidi Klum was presenting the finale of Germany's Next Top Model, after the bomb threat was called in at 9 pm (7pm GMT) on Thursday.

There was also concern over a suspicious suitcase near the cloakroom, which was later found not to have contained explosives, police said.

The rest of the arena was searched with a bomb-sniffing dog, but no further suspicious objects were found and the all clear was given around 1am.

Police said the investigation into the unidentified caller was ongoing and they could give no further information.

ProSieben said it had rescheduled the final for May 28. "ProSieben owes a final to its loyal viewers and finalists," it said in a statement.

Police said the audience of around 8,000 to 10,000 people left the SAP Arena calmly.

Newspaper Bild reported on its website that Klum, her daughter Leni and the show's jury had been taken to an undisclosed location outside the venue.

"Unfortunately we couldn't celebrate our big finale the way we had planned," Klum said on Facebook, adding a winner of the contest would be named within a few days.

Germany's Next Top model, a reality TV show based on model Tyra Banks' show America's Next Top Model, has faced some criticism in the 10 seasons it has been running, from groups saying it conveys unrealistic ideals of beauty to teenage viewers.

German regional media regulator MABB said this month it would initiate an investigation of the show's effect on teenagers following a complaint from activist group PinkStinks.

ProSieben has said it welcomed the scrutiny, saying that all independent regulators that had looked into the show so far had found it to be suitable for children aged six years and up.